Obey rule instance limit.

Do not show a rule type in the 'Add rule' dialog if the number of
current instances of that rule equals the max number of instances 
allowed by that rule type.

Bug: 25563007
Change-Id: I18f2598c6d92aec93c27755bb6b04c460ee294d0

src/com/android/settings/notification/ZenRuleInfo.java

@@ -12,4 +12,5 @@ public class ZenRuleInfo {
     public ComponentName serviceComponent;
     public boolean isSystem;
     public CharSequence packageLabel;
+    public int ruleInstanceLimit = -1;
 }